Semi-submersible tender

ABSTRACT

A multi-hull vessel having a grid for launching and retrieving watercraft supported between its sterns. A method for launching and retrieving watercraft from the vessel by ballasting the sterns down to immerse the watercraft-carrying grid and deballasting the sterns up to the normal operating draft.

United States Patent 1191 Marbury, Jr. Dec. 4, 1973 [5 SEMl-SUBMERSIBLE TENDER 2,405,115 8/1946 Creed 114 435 [75] Inventor: Fendall Marbury, Jr., North Chevy OTHER PUBLICATIONS h Md. C Flight Magazine January 17, 1935 page 81. [73] Assignee: Litton Systems, Inc., Beverly Hills,

Primary Examiner-Duane A. Reger 22 Filed; 2 1971 Assistant ExaminerGalen L. Barefoot Att0mey-A. C. Rose et al. [21] Appl. No.: 204,257 r [57] ABSTRACT [52] US. Cl. 114/435 51 Int. Cl B63b 35/50 A mum-hull vessel havmg a 8 v s and [58] Field 0': Search 114/435 "having waercraft SuPPMed between its Smms- A method for launching and retrieving watercraft from [56] References Cited the vessel by ballasting the stems down to immerse the UNITED STATES ATENTS watercraft-carrying grid and de-ballasting the stems 1 up to the normal operating draft; 3,403,652 10/1968 Hardy l l4/43.5 3,448,712 6/1969 Lehmann et a1 114/435 1 Claim, 3 Drawing figures MENTEU DEC 4 ma V L L SEMI-SUBMERSIBLE TENDER BACKGROUND OF THE INVENTION The present invention pertains to ships for launching or retrieving various types of watercraft such as lighters, barges or small boats.

In the prior art one type of ship for picking up aner hi s ly ratesi It Sl p- 2e12,; $2.1m:

ship shown therein has a boat well into which an auxiliary boat is floated and then ballasted down to rest on the boat well. Such a system requires that the boat to be retrieved have ballast tanks. The ballast tanks may be inappropriate for many types'of watercraft in that 7 they add undesired size and expense to the cost of the watercraft to say nothing of operating characteristics.

Another system for picking up barges onto a ship is illustratedin U. S. P at. No. 3 572,274 wherein thgstern 'iii'bifof the hulfsiifi drtzih inflatable and submersible pontoon for movement between a loading position in which the pontoon is floated or submerged in water in a stowed position in which the pontoon is located above the water surface. When. the pontoon ismoved to launching position, it is submerged in water and the barge is towed into the loading zone above the submerged-pontoon. The pontoon is thereupon inflated so that the upper surface engages the bottom? portion of the barge and seaway, compensating devices-are: operated to lift the pontoon to its stowed position whilethe barge is coupled or attracted to-thepontoon, forexarnple, by way of electromagnets. Such a system-for pickin the water which is an inefficient shape evenon .eimectedtmIv 5- buoyant member'is surmounted by a connecting strut.

smooth waterLWaves could therefore be cause a substantial loss of speed.

SUMMARY OF THE lN'YENTION The present invention overcomesth'ese and other dis= advantages of the priorart vby providing amuIti-hull' vessel having a platform for launching:anderetrieving watercraft-suspended from the vessel between theh'ulls at a location above the normal waterline 'of th'e. vessel.

The vessel is adapted to selectively submerge at least a 7 Connecting struts l6fand'18 unite above water hull portion 10 and submerge buoyant members 12 and 14' portion of the platform for launchingzand,retrieving-watercraft. In operation watercraft carried on thegrid are launched by ballasting the vessel down by v its st'erns until the platfonn is sufficiently submerged to immerse the watercraft to a draft which will supportflotation;

releasing the watercraft from the platform and floating it free; and ballasting the stems of themulti-hull' vessel: up to their normal draft. The watercraft areretrieved. by reversing the procedure.

art isdescribed in U. S.

No alterations in the-structure of the watercraft need a fixed grid, equipped if necessary with cradles to fit the type .of craft being handled. The amount of ballast required for launching and retrieving a watercraft is kept within reasonable limits because of the small waterplanes of the connecting struts.

The tender described herein can load or discharge a small craft in seas large enough to induce some motions in the craft being handled, and can carry out these operations while under way at a low speed. The tender,

with its clean hulls and great clearance, can maintain nearly full speed in rather high waves.

It is an object of the invention to provide a marine vessel capable of launching and retrieving watercrafts.

. It is another object of the invention'to provide a vessel for launching and retrieving watercraft while underway.

his still another object of the invention to provide a vessel. for launching and retrieving watercraft which requires no alterations to' the watercraft. 1

It is yet another object of the invention to provide a vessel for picking up watercraft entirely out of the water for maintenance and other purposes.

DESCRIPTION OF THE DRAWINGS FIG. I is a perspective view of the multi-hull vessel of the" invention.

FIG; 2 is a side view of the vesselwith its stems ballasted down.

FIG. 3 is a side view of the vessel carrying a watercraft- 1 DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring. nowto FIG. 1, the improved marine vessel of the. present inventioncomprises an above water portionlflgapairof submerged, buoyant membersl2 and IAtapair of connecting struts l6 and 18, anda water'- craft-carrying grid 20'. Shown in FIG. 1', the above water hull portion 10 is configured as a boattender while-it: may be generally of practically any shape. Un-

der-water'members 12 and l4'comprise a pair of elongated buoyant displacement bodies or members which may have a cylindrical'or non-cylindrical shape. Each Struts 16-and l8 are made buoyant'and have a length comparable to that of submerged members 12 and 14, buteither-may be longer than the other. The maximum beam 'of'struts 16am 1s isless than the beam of correv spending-submerged members 12 and 14. The waterplane: area of struts 16 and 18 is less than the maximum horizontal area of submerged members 12 and 14 forminimizing the amount of ballast required to ballast the stems with the vessel down as discussed in detail below.

into a floatable, marine vessel.

Connecting grid 20 is a fixed grid structure shown in FIG. 1 between the after ends of th'e'connectingstruts particular type of based craft' such as, for example, eradles 22 and 24 which are adapted to receive watercraft 26.

Each submerged, buoyant member and corresponding strut includes ballast tanks, such as for example,

ballast tanks 28, 30, 32 and 34. Each submerged member also includes a compartment 38 for fuel and a compartment 36 for machinery for propelling the vessel.

Launching a watercraft from the vessel is accomplished by the following method. The multi-hull vessel is ballasted down by its sterns until the grid 20 is sufficiently submerged to immerse the watercraft 26 to a draft which will support flotation. Watercraft 26 is next released from grid 20 or, if not restrained, it simply floats free. After the watercraft 26 floats free of grid 20, the stems of the multi-hull vessel are ballasted up to their normal operating draft of the vessel.

The method of launching a watercraft from the vessel may be carried out while the vessel is under way, preferably proceeding slowly into the prevailing waves. The multi-hull vessel is ballasted down by its stems until at least a portion of grid 20 is submerged. Dragging the after end of above water portion creates a slick over the cradles 22 and 24 of grid which will be somewhat smoother than the surrounding area of the sea. Control by the watercraft 26 over its horizontal position with respect to the stems of the multi-hull vessel and with respect to cradles 22 and 24 of grid 20 is established by steering the self-propelled watercraft 26 in the current passing through grid 20.

Retrieving a watercraft onto the multi-hull vessel is accomplished by the following method. The multi-hull vessel is ballasted down by its stems until at least a portion of grid 20 is submerged to a depth greater than the draft of the watercraft to be retrieved. Watercraft 26 is then maneuvered over grid 20. .Watercraft 26 is moored to the vessel while it is floating in a position over at least a portion of submerged grid 20. The watercraft 26 is then retrieved onto grid 20 by ballasting the stems of the multi-hull vessel up to their normal operating draft.

Watercraft 26 maybe retrieved while the vessel is underway. The self-propulsion and steering capabilities of the watercraft 26 are used to maneuver it in the current passing through grid 20 to control its horizontal position relative to the stems of the vessel and to cradles 22 or 24 of grid 20. Watercraft 26 is then moored to the vessel and landed on grid 20 and retrieved by deballasting the stems of the multi-hull vessel up to their normal operating draft.

The above-described methods of launch and recovery are especially suited to the type of double-hull ves- -sel shown in the drawings because the small waterplanes of the multi-hull vessel keep the required amount of ballast within reasonable limits. However, a vessel with double-hulls of more conventional shape can also be used.

I claim:

1. A marine vessel comprising:

a. A pair of submerged elongated buoyant members in a predetermined spaced relation including forward and aft ballast tanks for selectively varying thedraft and trend of said vessel;

b. An'above water hull portion in juxtaposition with said pair of submerged buoyant members;

0. A pair of elongated substantially vertical connecting struts, each said strut affixed to a corresponding submerged buoyant member and to said above water hull portion for uniting said pair of buoyant members and said above water hull portion into a floatable marine vessel; and

d. A platform comprising a grid permitting water to last tanks. 

1. A marine vessel comprising: a. A pair of submerged elongated buoyant members in a predetermined spaced relation including forward and aft ballast tanks for selectively varying the draft and trend of said vessel; b. An above water hull portion in juxtaposition with said pair of submerged buoyant members; c. A pair of elongated substantially vertical connecting struts, each said strut affixed to a corresponding submerged buoyant member and to said above water hull portion for uniting said pair of buoyant members and said above water hull portion into a floatable marine vessel; and d. A platform comprising a grid permitting water to flow therethrough whereby having minimized lift, for launching watercraft from said marine vessel and for retrieving watercraft thereto, said platform affixed to said marine vessel between said pair of connecting struts in a location above the normal waterline, and selectively capable of at least partial submergence by trimming said vessel with said ballast tanks. 